Spring counter-balance assemblies and solar trackers incorporating springs to balance rotation

ABSTRACT

A solar tracker assembly is provided which includes a support column, a torque tube or torsion beam connected to the support column, a mounting mechanism attached to the torque tube or torsion beam, a drive system connected to the torque tube or torsion beam, and a spring counter-balance assembly connected to the torque tube or torsion beam. An exemplary spring counter-balance assembly comprises a bearing housing and a bushing disposed within the bearing housing and configured to be slideably mounted onto the torque tube or torsion beam, and one or more compressible cords made of a flexible material. The compressible cords are located between the bushing and the bearing housing and provide damping during rotational movement of the solar tracker assembly. An exemplary spring counter-balance assembly is provided including at least one top bracket and at least one bottom bracket, at least one spring, a damper, and a bracket. An exemplary spring counter-balance assembly comprises a bearing housing and a bushing disposed within the bearing housing and configured to be slideably mounted onto the torque tube or torsion beam. The spring counter-balance assembly may include at least one coil spring and a rotational stop. The bushing may be made of an elastomeric material and define one or more air spaces.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/014,848 filed Sep. 8, 2020, now U.S. Pat. No. 11,533,017, issued Dec.20, 2022, which is a continuation of U.S. patent application Ser. No.15/909,142 filed Mar. 1, 2018, now U.S. Pat. No. 10,771,007, issued Sep.8, 2020, which claims priority to and the benefit of U.S. ProvisionalPatent Application Ser. No. 62/466,235, filed on Mar. 2, 2017, each ofwhich is hereby incorporated by reference in its entirety.

BACKGROUND Field

The present disclosure relates to spring counter-balance assemblies. Thepresent disclosure further relates to spring assemblies used to balancethe rotation of solar trackers and solar arrays

Description

Solar tracking systems are employed in photovoltaic and solar thermalapplications to increase the collection of sunlight by aiming thephotovoltaic panels or collectors at the sun throughout sun's dailymovement in the sky. In doing so, tracking systems incorporate pivotpoints or bearings on which to rotate. These bearings may be placed atthe center of gravity of the tracking system or may be locatedunderneath the photovoltaic or collector array.

The array balancing approach, the technique of placing the bearinghousings at or near the center of gravity of the array, has the benefitof alleviating the stress on the positioning drive apparatus becausethere is little or no overhung weight to create an inherent moment loadon the positioning system. Furthermore, balancing the mechanical systemabout the center of gravity also reduces or eliminates the torsiondeflection of the supporting structure, which may allow for lessstructure material requirements.

To counterbalance with a pivot point positioned at or near the center ofgravity of a tracking system, most designs must locate the pivot pointsabove the surface of the photovoltaic modules or thermal collectors.This creates complexity in the structure, in the bearing pivot points,and creates density inefficiencies because there must be spaces in thecollection surface where the bearings are located. The spaces where thecenter of gravity bearings are located are commonly referred to as deadspace in the system because solar collection is not possible at theseareas of the system. When used in a large photovoltaic solar farm orthermal collector, these dead spaces in the North/South length of thetracker row get multiplied by the East/West spacing that is requiredbetween the trackers and result in considerable density reduction acrossan entire field.

Accordingly, there is a need for an improved system for balancing therotation of a tracking system. There also is a need for an improvedbalancing system that eliminates dead spaces in the system. There is aneed for an improved balancing system that is less complex, requiresless structural material, and results in lower torsional deflection inthe system.

SUMMARY

Exemplary embodiments of the present disclosure alleviate to a greatextent the disadvantages of known balancing systems for solar trackersby incorporating spring elements in the solar tracker to counterbalancethe mechanical rotation instead of center of gravity pivot points. Thisprovides the advantage of keeping the pivot bearings and structureuncomplicated and requires no dead spaces in the system which results inall the benefits of a balanced structure without the penalty of deadspaces and fielded density inefficiencies. These benefits include lowcomplexity, less stress on the mechanical drive system, less structuralmaterial and less torsional deflection of the system and less stress onthe bearings themselves since they are located around the circumferenceof the torque transmitting structural member. More particularly,benefits include lower complexity in the bearings and structure relativeto the balanced center of gravity bearing system plus the attributes ofthe balanced CG system such as less stress on the mechanical drivesystem, less structural material and less torsional deflection of thesystem and elimination of the collector dead spaces to achieve highdensity.

Exemplary embodiments of a solar tracker assembly comprise a supportcolumn, a torque tube or torsion beam connected to the support column, amounting mechanism attached to the torque tube or torsion beam, a drivesystem connected to the torque tube or torsion beam, and a springcounter-balance assembly connected to the torque tube or torsion beam.One or more types of spring counter-balance assembly may be incorporatedinto the solar tracker assembly to balance its rotation.

Exemplary embodiments of a spring counter-balance assembly include atleast one top bracket and at least one bottom bracket, at least onespring, a damper, and a bracket. The spring has a first end and secondend. The first end of the spring is attached to the top bracket, and thesecond end of the spring is attached to the bottom bracket. The damperhas a first end and a second end. The first end of the damper isattached to the top bracket, and the second end of the damper isattached to the bottom bracket such that the damper is positionedsubstantially parallel to the spring. The bracket is attached to the topbracket and is sized and shaped for a torque tube or torsion beam to beinserted through the bracket such that the spring counter-balanceassembly can be incorporated into a solar tracker.

In exemplary embodiments, the spring is selected from the groupconsisting of: a drawbar spring, an extension spring, and a leaf spring.The spring may be incorporated into a damper, a damper bracket assembly,or a bearing housing. In exemplary embodiments, the solar trackerassembly is incorporated into a row of solar trackers wherein the springcounter-balance assembly comprises a first spring counter-balanceassembly connected to the torque tube or torsion beam at or near a firstend of the row and incorporating a first spring and a second springcounter-balance connected to the torque tube or torsion beam at or neara second end of the row and incorporating a second spring.

In exemplary embodiments, a solar tracker assembly comprises a supportcolumn, a torque tube or torsion beam connected to the support column, amounting mechanism attached to the torque tube or torsion beam, a drivesystem connected to the torque tube or torsion beam, and a springconnected to the torque tube or torsion beam. One or more solar modulesmay be mounted on the mounting mechanism. The spring may be a drawbarspring, an extension spring and/or a leaf spring.

In exemplary embodiments, the solar tracker assembly further comprises adamper bracket assembly attached to the torque tube or torsion beam, andthe spring is incorporated into the damper bracket assembly. Inexemplary embodiments, the solar tracker assembly further comprises atleast one damper attached to the torque tube or torsion beam, and thespring is incorporated into the damper. The solar tracker assembly mayhave at least one bearing housing attaching the torque tube or torsionbeam to the support column, and the spring may be located at the bearinghousing. In exemplary embodiments, the spring is incorporated into thebearing housing. The solar tracker assembly may further comprise atorque limiter assembly.

In exemplary embodiments, the solar tracker assembly further comprises aspring counter-balance assembly including at least one top bracket andat least one bottom bracket, at least one spring, a damper, and abracket mounting means. The spring has a first end and second end. Thefirst end of the spring is attached to the top bracket, and the secondend of the spring is attached to the bottom bracket. The damper has afirst end and a second end. The first end of the damper is attached tothe top bracket, and the second end of the damper is attached to thebottom bracket such that the damper is positioned substantially parallelto the spring. The bracket is attached to the top bracket and such thattorque tube or torsion beam is inserted through the bracket to connectthe spring counter-balance assembly to the torque tube or torsion beam.

Exemplary embodiments of a solar array comprise at least one trackerrow. Each tracker row includes at least one support column, at least onetorque tube or torsion beam connected to the support column, a mountingmechanism attached to the torque tube or torsion beam, a drive systemconnected to the torque tube or torsion beam, a first spring connectedto the torque tube or torsion beam at or near a first end of the row,and a second spring connected to the torque tube or torsion beam at ornear a second end of the row, where the second end is opposite the firstend. One or more solar modules may be mounted on the mounting mechanismsof the solar array. The spring may be a drawbar spring, an extensionspring and/or a leaf spring.

In exemplary embodiments, the solar array further comprises a damperbracket assembly attached to the torque tube or torsion beam, and thespring is incorporated into the damper bracket assembly. In exemplaryembodiments, the solar array further comprises at least one damperattached to the torque tube or torsion beam, and the spring isincorporated into the damper. The solar array may have at least onebearing housing attaching the torque tube or torsion beam to the supportcolumn, and the spring may be located at the bearing housing. Inexemplary embodiments, the spring is incorporated into the bearinghousing. The solar array may further comprise a torque limiter assembly.

The solar array may have a first spring counter-balance assemblyconnected to the torque tube or torsion beam at or near the first end ofthe row and incorporating the first spring and a second springcounter-balance connected to the torque tube or torsion beam at or nearthe second end of the row and incorporating the second spring. Eachspring counter-balance assembly comprises at least one top bracket andat least one bottom bracket, at least one spring, a damper, and abracket. The spring has a first end and second end. The first end of thespring is attached to the top bracket, and the second end of the springis attached to the bottom bracket. The damper has a first end and asecond end. The first end of the damper is attached to the top bracket,and the second end of the damper is attached to the bottom bracket suchthat the damper is positioned substantially parallel to the spring. Thebracket is attached to the top bracket and such that torque tube ortorsion beam is inserted through the bracket to connect the springcounter-balance assembly to the torque tube or torsion beam.

In exemplary embodiments, the spring counter-balance assembly comprisesan eccentric compression bushing configured to be slideably mounted ontothe torque tube or torsion beam, a shaped outer bearing housingconfigured to be mounted over the eccentric compression bushing, and ormore compressible cords made of an elastomeric material. The eccentriccompression bushing and the shaped outer bearing housing and may providedamping during rotational movement of the solar tracker assembly. Theflexible material of the compressible cords may be rubber or anotherelastomer. In exemplary embodiments, the bushing has an octagonal innersurface with one or more substantially flat surfaces, and the bearinghousing hays one or more lobes such that one or more spaces are definedbetween the substantially flat surfaces and the lobes. The compressiblecords may be disposed in the spaces between the substantially flatsurfaces and the lobes.

In exemplary embodiments, the bushing has an octagonal innercross-section and a substantially circular outer cross-section with fourlobes. The bearing housing may be substantially square shaped, and thespring counter-balance assembly allows up to at least plus or minus 45degrees of rotation of the torque tube or torsion beam. In exemplaryembodiments, the bushing has an octagonal inner cross-section and asubstantially triangular outer cross-section with three lobes, and thespring counter-balance assembly allows up to at least plus or minus 60degrees of rotation of the torque tube or torsion beam. The outerbearing housing is one of: substantially square shaped, substantiallyhexagonal, and substantially circular with three lobes.

Exemplary embodiments of a spring counter-balance assembly include abearing housing having one or more lobes, a bushing disposed within thebearing housing such that one or more spaces are defined between thebushing and the lobes, and one or more compressible cords made of aflexible material. The compressible cords are disposed in the spacesbetween the bushing and the lobes.

In exemplary embodiments, the spring counter-balance assembly comprisesa bearing housing and a bushing disposed within the bearing housing andconfigured to be slideably mounted onto the torque tube or torsion beam.The spring counter-balance assembly may further comprise at least onecoil spring and a rotational stop. The bushing may be made of anelastomeric material and define one or more air spaces. In exemplaryembodiments, the spring counter-balance assembly further comprises atleast one rotational stop. The bearing housing may be made of anelastomeric material and further comprise at least one rotational stop.

Accordingly, it is seen that spring counter-balance assemblies andbalancing systems for solar trackers and solar arrays are provided. Thedisclosed assemblies, systems, and methods provide improved balancingsystems that eliminate dead spaces, reduce complexity, require lessstructural material, minimize drive forces, and result in lowertorsional deflection. These and other features and advantages will beappreciated from review of the following detailed description, alongwith the accompanying figures in which like reference numbers refer tolike parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned features and objects of the present disclosure willbecome more apparent with reference to the following description takenin conjunction with the accompanying drawings wherein like referencenumerals denote like elements and in which:

FIG. 1 is a perspective view of an exemplary embodiment of a solartracker assembly in accordance with the present disclosure;

FIG. 2A is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure;

FIG. 2B is a side view of the spring counter-balance assembly of FIG.2A;

FIG. 3 is a side view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure shownmounted on a torque tube or torsion beam;

FIG. 4 is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure shownmounted on solar tracker assembly;

FIG. 5A is a perspective view of an exemplary embodiment of an extensionspring counter-balance assembly in accordance with the presentdisclosure;

FIG. 5B is a side view of the extension spring counter-balance assemblyof FIG. 5A;

FIG. 6 is a perspective view of an exemplary embodiment of an extensionspring counter-balance assembly in accordance with the presentdisclosure shown mounted on a torque tube or torsion beam;

FIG. 7 is a side view of an exemplary embodiment of an extension springcounter-balance assembly in accordance with the present disclosure shownmounted on a torque tube or torsion beam;

FIG. 8 is a side view of an exemplary embodiment of an extension springcounter-balance assembly in accordance with the present disclosure shownmounted on solar tracker assembly;

FIG. 9 is a perspective view of an exemplary embodiment of an extensionspring counter-balance assembly in accordance with the presentdisclosure shown mounted on solar tracker assembly;

FIG. 10 is a cross-sectional view of an exemplary embodiment of anintegrated spring counter-balance bearing assembly in accordance withthe present disclosure;

FIG. 11 is a cross-sectional view of an exemplary embodiment of anintegrated spring counter-balance bearing assembly in accordance withthe present disclosure;

FIG. 12 is a side view of an exemplary embodiment of an integratedtorsional spring counter-balance bearing assembly in accordance with thepresent disclosure;

FIG. 13A is a top view of an exemplary embodiment of a bearing housingof a spring counter-balance assembly in accordance with the presentdisclosure;

FIG. 13B is a side view of an exemplary embodiment of the torsionalspring bearing insert of FIG. 13A in accordance with the presentdisclosure;

FIG. 14A is a perspective view of an exemplary embodiment of anintegrated spring counter-balance bearing assembly in accordance withthe present disclosure;

FIG. 14B is a front cross-sectional view of the integrated springcounter-balance bearing assembly of FIG. 14A;

FIG. 14C is a detail view of a corner of the integrated springcounter-balance bearing assembly elastomer space of FIG. 14A;

FIG. 15A is a perspective view of an exemplary embodiment of a bearinghousing of a spring counter-balance assembly in accordance with thepresent disclosure;

FIG. 15B is a front view of the bearing housing of FIG. 15A;

FIG. 15C is a side view of the bearing housing of FIG. 15A;

FIG. 15D is a top view of the bushing of the bearing assembly of FIG.14A;

FIG. 16A is a perspective view of an exemplary embodiment of a bushingof a spring counter-balance assembly in accordance with the presentdisclosure;

FIG. 16B is a front cross-sectional view of the bushing of FIG. 16A;

FIG. 17A is a perspective view of an exemplary embodiment of acompressible cord of a spring counter-balance assembly in accordancewith the present disclosure;

FIG. 17B is a front cross-sectional view of the compressible cord ofFIG. 17A;

FIG. 17C is a side view of the compressible cord of FIG. 17A;

FIG. 17D is a top view of the compressible cord of FIG. 17A;

FIG. 18A is a front cross-sectional view of an exemplary embodiment of aspring counter-balance assembly in accordance with the presentdisclosure shown without the compressible cords;

FIG. 18B is a front cross-sectional view of the spring counter-balanceassembly of FIG. 18A shown in rotation;

FIG. 18C is a front cross-sectional view of the spring counter-balanceassembly of FIG. 18A shown in rotation;

FIG. 19 is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure;

FIG. 20A is a front cross-sectional view of an exemplary embodiment of aspring counter-balance assembly in accordance with the presentdisclosure;

FIG. 20B is a front cross-sectional view of the spring counter-balanceassembly of FIG. 20A shown in 30-degree rotation;

FIG. 20C is a front cross-sectional view of the spring counter-balanceassembly of FIG. 20A shown in 52-degree rotation;

FIG. 21 is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure shownmounted on a torque tube or torsion beam;

FIG. 22 is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure shownmounted on solar tracker assembly;

FIG. 23A is a front cross-section view of an exemplary embodiment of aspring counter-balance assembly in accordance with the presentdisclosure

FIG. 23B is a front cross-sectional view of the spring counter-balanceassembly of FIG. 23A shown in rotation;

FIG. 23C is a front cross-sectional view of the spring counter-balanceassembly of FIG. 23A shown in rotation;

FIG. 24 is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure shownmounted on a torque tube or torsion beam; and

FIG. 25 is a perspective view of an exemplary embodiment of a springcounter-balance assembly in accordance with the present disclosure shownmounted on solar tracker assembly.

DETAILED DESCRIPTION

In the following paragraphs, embodiments will be described in detail byway of example with reference to the accompanying drawings, which arenot drawn to scale, and the illustrated components are not necessarilydrawn proportionately to one another. Throughout this description, theembodiments and examples shown should be considered as exemplars, ratherthan as limitations of the present disclosure. As used herein, the“present disclosure” refers to any one of the embodiments describedherein, and any equivalents. Furthermore, reference to various aspectsof the disclosure throughout this document does not mean that allclaimed embodiments or methods must include the referenced aspects.

Solar trackers incorporating one or more spring counter-balanceassemblies will now be described. The spring counter-balance assembliesdescribed herein are designed to allow a large degree of rotation andcounterbalance the overhung weight of the collectors mounted to thetorque tube or torque beam assembly. As shown in FIG. 1 , an exemplarysolar tracker assembly 12 comprises at least one support column 32,which may be any shape and composed of any material so long as it iscapable of supporting the PV modules or collectors mounted thereto.Exemplary embodiments of a solar tracker assembly 12 include twospaced-apart support columns 32. A torque tube or torsion beam 34 orother tracker structure is connected to the support column. Moreparticularly, the torsion beam 34 bridges the two support columns andmay be attached to the support columns 32 by a bearing housing 36 andbearing housing arrangement including any suitable fasteners.

The torque tube or torsion beam 34 may be any shape or configurationsuitable for supporting a mounting rack or other mounting mechanism,including multiple connected beams, and in exemplary embodiments it hasa circular-, square- or hexagonal-shaped cross section. It should benoted that the torque tube or torsion beam 34 could be anycross-sectional shape including but not limited to circular, rounded,ovular, square, rectangular, triangular, pentagonal, hexagonal, andoctagonal. In a system that has overhung weight, the overhung loadtorque varies as the system rotates.

A pivot axis 40 extends through the torque tube or torsion beam 34,which may pivot or rotate about the pivot axis 40. Solar modules 42 maybe mounted to the solar tracker 12, either mounted on the torque tube ortorsion beam 34 using clamps or mounting brackets 35 or on the mountingrack via a module mounting bracket assembly or other mounting device. Itshould be noted that solar trackers could employ more than one torquetube or torsion beam in a double- or multiple-beam torsion structurearrangement. In such embodiments, a tracker would have two or moretorsion beams running along its length. A row of multiple trackers couldhave two or more torsion beams running along the length of the row.

A mounting rack (not shown) is attached to the torque tube or torsionbeam 34. In exemplary embodiments, the mounting rack includes a frontframe support and rear frame support (not shown). The front framesupport is disposed upon a first side of the torque tube or torsionbeam, and the rear frame support is disposed upon a second opposite sideof the torque tube or torsion beam.

The solar tracker 12 may have a gear-driven mechanical system whichincludes a gear rack 14. The mechanical system may also include a geardrive system 16 that incorporates a torque limiter 18 such as a torquelimiting clutch. A motor 15 may be provided to drive the gear drivesystem 16, which in turn rotates the torsion beam or torque tube 34directly, or drives a gear rack 14, which in turn drives the torque tubeor torsion beam 34 or another module mounting beam structure. The gearrack 14 may be a spur gear rack or D-ring chain drive, which is affixedto the rotatable torque tube or torsion beam of the tracker. Thus, whenactivated by gear drive system, the tracker is rotated. A second, third,etc. mechanical unit, similar to tracking assembly 12 can be connectedto drive shaft 25 with a separate and similar worm assembly. This can berepeated for several mechanical units in a gear-driven mechanicalsystem.

Exemplary solar tracker assemblies 12 may further comprise one or moredampers 58 incorporated at or near the gear rack to control the releaseof torsional force and slow the motion of the solar tracker assembly.The dampers 58 may serve double duty as stops at the end of the array,or dampers placed at any location may be designed to assist inregulating the torsional release reaction speed and resisting the hingemoment loads. In exemplary embodiments, a spring is integrated into atleast one of the dampers. An additional bracket may be provided whichallows a damper 58 to be connected between the torsion tube 34 and thesupport column 32 of the tracker 12. A damper 58 may be incorporated atthe gear drive to control the rate at which the tracker rotates duringan over torque release event. When the torsion is relieved by allowingthe system to rotate, the speed at which the array is allowed to movemay be controlled by the slip friction of the clutch, or by an externaldamper or both. A spring may be incorporated into one or more of thedamper brackets.

With reference to FIGS. 2A-9 , exemplary embodiments of springcounter-balance assemblies 10 and 10 a will now be described. Exemplaryembodiments of a spring counter-balance assembly include a top bracket62, a bottom bracket 64, a damper 66, a bracket 68, and a spring 70,which may be a drawbar spring, an extension spring, a leaf spring, orany other suitable type of spring. The spring 70 is located between thetop bracket 62 and the bottom bracket 64. More particularly, the firstend of the spring 70 is directly or indirectly attached to the topbracket, and the second end of the spring 70 is directly or indirectlyattached to the bottom bracket 64. As best seen in FIGS. 2A and 2B,spring holders 72 may be used to link the spring 70 to the top andbottom brackets 62, 64. Alternatively, as best seen in FIGS. 5A and 5B,the spring 70 of spring counter-balance assembly 10 a may be directlyconnected to the top and bottom brackets 62, 64.

In exemplary embodiments, damper 66 is positioned substantially parallelto the spring 70. More particularly, the first end of the damper 66 isattached to the top bracket 62, and the second end of the damper 66 isattached to the bottom bracket 62. In exemplary embodiments, a bracket68 is attached to the top bracket 62 and is sized and shaped for atorque tube or torsion beam 34 to be inserted through the bracket. Thisconfiguration of the bracket provides for quick and easy attachment totorque tube or torsion beam and incorporation of the springcounter-balance assembly into a solar tracker. It should be noted thatmore than one bracket 68 could be used, and exemplary embodiments employtwo or more brackets 68 for mounting the spring counter-balance assemblyto the torque tube or torsion beam 34. Counterbalance springs anddampers may also be mounted by separate brackets onto the supportcolumns in the same or different locations with similar effectiveness(not shown).

As shown in FIGS. 3-4 and 6-9 , an extension spring counter-balanceassembly 10 or 10 a may be incorporated into a solar tracker byattachment of the spring counter-balance assembly to the torque tube ortorsion beam of the tracker. As mentioned above, the springcounter-balance assembly 10 is connected to the solar tracker via one ormore brackets 68 on the top frame of the assembly. More particularly,because the bracket is sized and shaped to fit onto the torque tube ortorsion beam, it can slide onto the torque tube or torsion beam (or thetube or beam inserted though the opening of the bracket) to attach thespring counter-balance assembly to the tracker. As best seen in FIGS. 4,6 and 9 , the spring counter-balance assembly also may be secured to thesupport column at one or more locations using lower brackets 74. Moreparticularly, the top frame may include a pin, threaded fastener, orother type of fastener to attach it to a top portion of the supportcolumn and/or the bottom frame may have one or more additional lowerbrackets 74 that fit around the support column and attaches it theretoat a location at or near the bottom of the support column.

In exemplary embodiments, a counter-balance assembly 10 or 10 a may beincorporated into a solar array comprising one or more rows of solartrackers. The solar array may include individually motorized trackerswithout mechanical linkages between the rows. The array may include aplurality of rows of solar trackers comprised of multiple rows of linkedsolar trackers. More particularly, multiple solar trackers may bemechanically linked in a large array configuration so they may operatein unison, driven by a single motor and tracker controller. In exemplaryembodiments, one spring is connected to the torque tube or torsion beamat or near the first end of the tracker row, and another spring isconnected to the torque tube or torsion beam at or near the second endof the row. As discussed above, each spring may be incorporated into aspring counter-balance assembly or into a damper or bearing housingassembly.

Exemplary embodiments include a configuration in which two drawbarsprings are placed toward the ends of the tracker row. The drawbarsprings may be incorporated into the damper bracket assembly or locatedseparately from the dampers with a separate bracket. Exemplaryembodiments include a configuration in which two compression drawbarsprings are placed toward the ends of the tracker row. The compressiondrawbar springs may be incorporated into the damper bracket assembly orlocated separately from the dampers with a separate bracket. Exemplaryembodiments include a configuration in which two leaf springs are placedtoward the ends of the tracker row (not shown). The leaf springs may beincorporated into the damper bracket assembly or located separately fromthe dampers with a separate bracket. In exemplary embodiments, smallerdrawbar, extension or leaf springs may be located at each bearinghousing. Springs also could be integrated into the stop blocks of thebearing housings. Exemplary trackers may include torsional spring pivotpoints that integral to the bearing housings and/or torsional springpivot points that are not integral to the bearing housings butcounterbalance movement.

Solar trackers incorporating the non-elastomeric spring counter-balanceassembly embodiments described above typically will have inherentdamping mechanisms. Dampers and their use in solar trackers aredescribed in detail in U.S. Pat. No. 9,581,678, issued Feb. 28, 2017,which is hereby incorporated by reference in its entirety. As best seenin FIG. 1 , exemplary solar trackers may comprise a damper incorporatedat or near the gear rack to control the release of torsional force andslow the motion of the solar tracker assembly. A damper may beincorporated at the gear drive to control the rate at which the trackerrotates during an over torque event. The max angle stop may then beresisted not only by the gear rack, but by the dampers at the gear rackor stops at the end of the rows of solar trackers 12, thereby sharingthe torsion load of the gear rack 60 and distributing the torsion loadthrough multiple points on the torsion tube 34. The dampers 58 may servedouble duty as stops at the end of the array, or dampers placed at anylocation may be designed to assist in regulating the torsional releasereaction speed and resisting the hinge moment loads.

Turning now to FIG. 10 , an exemplary embodiment of an integrated springcounter-balance assembly employing discrete coil springs and arotational stop will now be described. Spring counter-balance assembly110 does not provide inherent damping, and an additional damper may berequired to control speed of movement or oscillation. Springcounter-balance assembly 110, shown in cross-section, has a housing 162including an upper rounded section 166 which is slid onto a torque tubeor torsion beam of a solar tracker and a lower section 168. An innerlayer 174 of aluminum or other suitable structural material is disposedwithin the top section 166 of the housing 162, and there is a circularpolymer bearing material layer 167 between top section 166 and innerlayer 174. The inner surface of the inner layer 174 is sized and shapedto fit over a torque tube or torsion beam of a solar tracker. Inexemplary embodiments, the inner surface of the inner layer 174 has anoctagonal cross-section, and the outer surface has a substantiallycircular cross section.

The lower section 168 of the housing 162 contains two coil springs 170,a stop block 164 and has a bottom surface for incorporating mountingbolts 172 or other fastening mechanisms. More particularly, the stopblock 164 is located in the center of the spring counter-balanceassembly 110 directly below the below the inner layer 174. The stopblock 164 is flanked on each side by coil springs 170, with one coilspring 170 adjacent to the right side of the stop block 164 and theother coil spring 170 adjacent to the left side of the stop block 164.This double spring and stop design of spring counter-balance assembly110 advantageously limits rotation of a torque tube or torsion beamalong its angle of rotation 176 in two ways. Each coil spring 170provides rotational resistance, and depending on the direction of therotation, either the coil spring on the right side or the coil spring onthe left side can bottom out in compression. Also, when the torque tubeor torsion beam rotates, rotation may be limited when the stop block 164hits the side of the lower section 168 of the housing 162 of the springcounter-balance assembly 110.

FIG. 11 illustrates an exemplary embodiment of a spring counter-balanceassembly with a radial elastic bushing. This embodiment may also provideinherent damping due to the elastomers lack of spring hysteresis. Springcounter-balance assembly 210 comprises a housing 262 that has a stop 264as part of the internal structure of the housing itself. In exemplaryembodiments, the housing 262 is made of aluminum, cast iron, or anothersuitable structural material. Disposed within the housing 262 is asubstantially round intermediate layer 270 composed of an elasticpolymer material. The intermediate polymer layer 270 defines one or moreair spaces 272 disposed within it. In exemplary embodiments, there are aplurality of air spaces 272 spaced apart and extending around thecircumference of the intermediate layer 270. A coupler 266, which may bea metal tube cast in elastomer, is disposed adjacent the inner surfaceof the intermediate layer 270. The coupler 266 is sized and shaped to beslid over a torque tube or torsion beam of a solar tracker and, inexemplary embodiments, has an octagonal cross-section.

In exemplary embodiments, housing 262 is substantially circular withextending sides and a substantially flat base. It is designed to have astop 264 at the bottom of the circular portion housing the intermediatelayer 270 and the metal tube 266. Housing 262 also has a center rib 274in its base portion located directly below the stop 264. Exemplaryembodiments include at least one rotational stop 268 on the coupler 266.A rotational stop 268 may be located at each of the bottom corners ofeach lateral side of the coupler 266. Housing 262 advantageously rotateswithout any sliding surfaces. Rather, as a torque tube or torsion beamrotates about its angle of rotation 276 (also 54, shown in FIG. 1 ), thespring counter-balance assembly 210 flexes in the intermediate elastomerlayer and provides rotational spring force. When the torque tube ortorsion beam rotates to its limit, one of the rotational stop 268 on thecoupler 266 hits the stop 264 of the housing 262. The elastomer betweenthe metal stops acts a soft stop for rotation.

With reference to FIGS. 12, 13A and 13B, a spring counter-balanceassembly with an integral longitudinal elastomer torsion spring andsurface bearings which provides inherent damping will now be described.Spring counter-balance assembly 310 comprises a bearing housing 362 andan inner elastomer tube 374 bonded to two octagonal shaped metal orplastic inserts at each end of the elastomer tube 374 rotating on apolymer bearing layer 367 inside the bearing housing 362. An exemplarybearing housing 362 includes an upper rounded section 366 and a lowersection 368 that has a bottom surface for incorporating mounting bolts372 or other fastening mechanisms. The housing 362 is made of aluminum,cast iron, engineered polymer or other suitable structural material. Theupper and lower sections 366, 368 are connected, and the full housing362 forms a circular interior. Circular bearing layers 367 is disposedat the ends of the interior of the housing 362 and is made of a polymerbearing material. The inner elastomer torsion tube 34 has an outersurface with a substantially circular cross-section mating to a circularpolymer bearing material 367 and an inner surface sized and bonded totwo shaped inserts at each end to be slid onto and rotationally keyed toa torque tube or torsion beam 34. In exemplary embodiments, the innersurface has an octagonal cross-section.

The elastomer torsion tube layer 374 has at least one integrally formedprotrusion that keys to the bearing housing 362. In exemplaryembodiments, the torsion tube 34 is held fixed to the bearing housing362 at the center while each end is keyed to the torque tube or torquebeam. In this embodiment, the torsion tube twists the elastomer torsionspring 374 relative to the bearing housing creating a counterbalancerotational force as it turns in either direction. The elastomer torsiontube 374 is anchored into the housing 362 by anti-rotation tabs 376 thatinterlock into holes in the upper section 366 of the housing 362.Rotational stops 364 engage the bearing housing 362 at notches 365 whenthe desired rotational angle limit is achieved. The design of springcounter-balance assembly 310 advantageously minimizes the diameter ofthe assembly by configuring the torsion spring layer 374 parallel to theaxis of rotation. More particularly, the stops 364 and the bearing endsof surface of the inner structural layer 374 is located at the ends ofthe housing 362 and keyed to the shape of torque tube or torsion beam atthose ends. The keyed ends are molded to an elastomer tube, which isconnected to the housing 362 at the center.

Turning now to FIGS. 14A-17D, spring counter-balance assemblies whichprovide counter-balance spring force and inherent damping will now bedescribed. As discussed in detail herein, spring counter-balanceassembly 410 incorporates one or more compressible cords 478 to provideboth rotational counter-balance spring force and damping capability. Inexemplary embodiments, the compressible cords 478 are made of a flexiblematerial, which may be an elastomeric material such as rubber. The lackof hysteresis of the rubber or other elastomeric material providesnatural damping, in some cases obviating the need to employ a damper.The compressible cords are incorporated into an assembly having asubstantially square bearing housing and a substantially roundedbushing. The assembly 410 is designed to allow a large degree ofrotation and counterbalance heavy objects such as solar trackersmounting solar modules. More particularly, the square design allowsrotational movement up to plus or minus approximately 48 degrees ofrotation.

The assembly 410 includes bushing 470, which is sized and shaped suchthat it can be slid onto a torque tube or torsion beam, or so a torquetube or torsion beam can be slid through the bushing 470. The innersurface 472 of the bushing 470 can be any suitable shape to correspondto the cross-sectional shape of the torque tube or torsion beam. Inexemplary embodiments, the inner surface 472 of the bushing 470 has anoctagonal shape and the outer surface 480 is substantially round withfour lobes 486 to compress the compressible cords 478 as it rotates.Spring counter-balance assembly 410 also includes bearing housing 476.The bushing 470 is disposed within the bearing housing 476 andcompressible cords 478 situated between bushing 470 and bearing housing476. Bearing housing 476 can be any suitable shape, and in exemplaryembodiments is substantially square-shaped with four rounded corners.

In exemplary embodiments, bushing 470 is disposed within bearing housing476 along with four compressible cords 478, each compressible cord beinglocated adjacent a corner 484 of the bearing housing 476. Moreparticularly, as best seen in FIGS. 14A and 14B, when bushing 470 isdisposed with bearing housing 476 there are four spaces 482 definedbetween the outer surface 480 of the bushing and the inner surface ofthe rounded corners 484 of the bearing housing. Each compressible cord478 is located in a space 482 such that the compressible cords aresecurely disposed between the bushing 470 and the bearing housing 476.The generally rounded four lobes of the outer surface 480 of bushing 470may have flat sections 488 situated to correspond with spaces 482 suchthat the compressible cords 478 rest on the flat sections of thebushing.

As best seen in FIG. 16B, in exemplary embodiments, bushing 470 has arelatively thinner cross-section at each flat section 488 than arelatively thicker cross section at the more lobes 486 of the bushing,and the outer surface 480 of the bushing alternates between flatsections 488 and more rounded sections, or lobes 486. The thinner crosssections are designed to accommodate the compressible cords 478 at theflat sections 488 of the bushing 470. As best seen in FIGS. 16A and 16B,each flat section 488 of the bushing 470 may define a transition 490from one lobe 486 to an adjacent lobe 486.

As the bushing 470 rotates, the compressible cords 478 both roll andcompress to provide a counterbalance rotational spring force. This forceis a function of the durometer (hardness) of the elastomer and the shaperelationship of the bushing 470 and bearing housing 476 that entraps thecompressible cords 478. In this embodiment, the spring bearing isdesigned to counteract the overhung rotational weight of the devicesmounted on the torque tube or torsion beam. The overhung weight is asine function of the rotational angle, weight and the distance of theweight from the center of rotation. It is therefore advantageous todesign the spring force profile of the elastomer spring bearing assemblyto provide a resistance profile as close to a sine function of therotational angle which corresponds to the amplitude of the torque as aresult of the moment forces generated by the collectors mounted on thetorque tube or torsion beam.

Spring counter-balance assembly 410 advantageously allows up to + or −48degrees of rotation and benefits from a small outside envelope and fourcompressible cords. Applications requiring + or −48 degrees of rotationmay benefit from this design due to its small radius from the centerrotating point which minimizes the overhung weight and the sharing ofthe spring and damper loads with four compressible cords.

As shown in FIGS. 18A-22 , another exemplary embodiment of a springcounter-balance assembly 510 provides inherent damping by incorporatingcompressible cords 576 in a circular tri-lobed bearing housing and amodified Reuleaux triangular bushing 570. In some applications, up to +or −63 degrees of rotation are required, which assembly 510 canfacilitate.

When the torque tube or torsion beam 34 of the solar tracker assembly 12rotates, the damper cords 578 compress as the bushing 570 rotates aboutangle of rotation 592 and the bearing housing 576 remains in a fixedposition. More particularly, when the bushing 570 rotates and the threelobed sections 586 of the bushing shift in position against a stationarybearing 576, each damper cord 578 is compressed between the inner wallof the bearing housing 576 and the lobed surface 586 of the bushing 570as the space 582 diminishes in size due to the changed position of eachlobed section 586. As the compressible cords 578 reach their maximumcompressibility, they provide rotational spring force and damping uponcompression release due to the lack of hysteresis of the elastomericmaterial. The compressible cords 578 may be made of a flexible material,which may be an elastomeric material such as rubber. The inherent lackof hysteresis of the rubber or other elastomeric material providesnatural damping, obviating the need to employ a damper. The assembly 510is designed to allow a large degree of rotation and counterbalance theoverhung moment loads from objects such as solar trackers mounting solarmodules.

Spring counter-balance assembly 510 includes bushing 570, which is sizedand shaped such that it can be slid onto a torque tube or torsion beam,or so a torque tube or torsion beam can be slid through it. In exemplaryembodiments, the inner surface 572 of the bushing 570 has an octagonalshape. Bushing 570 has a substantially triangular cross-section, and theouter surface 580 has three predominantly flat sections 588 constitutingthe sides of the triangle and three rounded sections, or lobes 586constituting the angles of the triangle. Bearing housing 576 has asubstantially hexagonal cross-section with six flat side sections 574and six angled corners 584. The bearing housing 576 may be designed suchthat the corners are not all equal in their angles. In an exemplaryembodiment, the bottom corner has a smaller angle than the top corner.

In exemplary embodiments, bushing 570 is disposed within the bearinghousing 576 such that each of the lobes 586 of the bushing 570 islocated adjacent one of three alternating internal angled corners 584 ofthe bearing housing 576. As best seen in FIG. 18A, in this configurationof the assembly 510, each flat section 588 of the bushing 570 is locatedfacing one of the other three alternating internal angled corners 584 ofthe bearing housing 576 such that a space 582 is defined between eachflat section 588 and each internal angled corner 548.

Bushing 570 could be used with another embodiment of bearing housing 676shown in FIGS. 23A-25 . In this variation of the spring counter-balanceassembly 510 a, the bearing housing 676 is substantially circular withthree lobes 686, and the bushing 570 disposed within the bearing housing676 such that each of the three predominantly flat section 588 of thebushing 570 is located facing one of the lobes 686 such that a space 582is defined between each flat section 588 and each lobe 686.Incorporating a generally round bearing housing with three lobes entrapsthe compressible cords better than the hexagonal design at the largerotational angles.

As the bushing 570 rotates, the compressible cords 578 both roll andcompress into a smaller space which results in a counterbalancing springforce. Since the overhung weight of the apparatus mounted on the torquetube or torsion beam 34 creates a moment force about the center of therotation axis, the spring design is optimally constructed to equallycounteract the moment force created by the apparatus as it rotates. Thecounterbalance force is a moment force about a centroid and therefore isa sine function of the angle of rotation. The moment force created bythe overhung weight of the apparatus equals sin*angle*weight*distancefrom centroid. This describes a sine function with amplitude. To designthe corresponding equal counterbalance force, the shape of resultingrotational spring force should be a sine function and to derive thedesired amplitude is a result of the compression of the compressiblecords during rotation and their corresponding resistance to compression,otherwise known as their hardness measured as durometer. The durometerof the elastomer, its characteristics as it compresses and the geometricshape relationship of the bushing and bearing housing that entraps thecompressible cords are the variables that interrelate to achieve thedesired counterbalance amplitude to approximate a sine function momentforce resistance curve.

In exemplary embodiments, compressible cords 578 are situated betweenbushing 570 and bearing housing 576. In exemplary embodiments, there arethree compressible cords 578, each compressible cord being locatedadjacent an internal angled corner 584 of the bearing housing 576. Moreparticularly, as best seen in FIG. 20A, each compressible cord 578 islocated in one of the three spaces 582 defined between the three flatsections 588 of the bushing 570 and the internal angled corner 584 ofthe bearing housing 576. Each compressible cord 578 is located in aspace 582 such that the compressible cords are securely disposed betweenthe bushing 570 and the bearing housing 576.

Spring counter-balance assembly 510 advantageously allows a large degreeof rotation of a solar tracker 12, which can reach up to 126 degrees, orplus or minus at least 63 degrees. When the torque tube or torsion beam34 of the solar tracker assembly 12 rotates, the bushing 570 rotates,the bearing housing 576 remains in a fixed position, and the dampercords 578 compress. More particularly, when the bushing 570 rotatesabout axis of rotation 592 and the lobed sections 586 of the bushingshift in position relative to the stationary bearing 576, each dampercord 578 is compressed between the inner wall and each angled corner 584of the bearing 576 and the edge of a lobed section 586 of the bushing570 as the space 582 diminishes in size due to the changed position ofeach rounded section 586. As the compressible cords 578 reach theirmaximum compressibility, they provide dampening because of the lack ofhysteresis of the rubber material. Furthermore, as the compressiblecords 578 reach their designed rotational limit, further rotation ispossible but the resistance to rotation can be designed to increasedramatically as the rotation exceeds the limit value which will create asoft stop for the rotation of the system.

Exemplary embodiments of spring counter-balance assemblies describedherein, when used in conjunction with torsion limiter designs of a solartracker allow the torsion limiter to release the torsion purely as afunction of the wind induced torque instead of a function of the windplus the overhung weight induced torque in the system. This allows formore precise control over the torsion release and minimizes the velocityand damping necessary in the system since the overhung weight of thesystem is no longer applied to the torsion limiter and is not additiveto the torsion force or resulting release velocity.

Exemplary embodiments of spring counter-balance assemblies used with atorsion limiter eliminate the need for dead spaces and increases thedensity and overall land use efficiency of the power plant. When used inconjunction with a torque limiter they enable the torque limiter toreact more precisely and predictably because the position of the trackerand the variable of the overhung weight do not play a part in the torqueapplied to the limiter. They also reduce the velocity of the trackersystem during torque release since the additive variable overhung weightdo not add to the dynamic load once the torsion release is in motion.Exemplary designs reduce the impact load by counterbalancing the weightand may also create a soft stop when engaging the mechanical stops onthe tracker bearings.

Torsion limiters, torque limiters, torsion limiting clutches, and solartrackers incorporating torsion and torque limiters are described indetail in U.S. Pat. No. 9,581,678, issued Feb. 28, 2017, which is herebyincorporated by reference in its entirety. An exemplary gear drivesystem comprises a torque limiting clutch and a gear assembly includingat least one gear wheel. In exemplary embodiments, the gear drive systemof the solar tracker incorporates a torque-limiting clutch on the firstgear stage of the solar tracker. Exemplary embodiments could include asingle-stage gear-driven solar tracker where the gear drive system is asingle-stage worm gear drive that directly rotates the solar collectorarray. The gear assembly may include a one-way gearbox and the torquelimiter may be a torque limiting clutch contained within the gearbox.The torque limiter, in the form of a clutch, could be located betweenthe connection of the output of the worm gear drive and the solarcollector array. Exemplary embodiments also include two- or multi-stagesolar trackers. Gear assembly includes at least one gear wheel, and inexemplary embodiments the gear wheel is a worm wheel.

In exemplary embodiments, the torque limiting clutch is located betweenthe connection of the output of the first stage worm gear and the secondstage gear. The torque-limiting clutch may be located at an output ofthe gear assembly, on the output of the first gear stage of the solartracker, and prior to a location where the gear drive system engages thegear rack of the solar tracker. The clutch may be located at two tapersections of the worm wheel gear. The two steel tapers engage the wormwheel gear under spring tension, which may be adjustable via a nut orother adjustment mechanism. Instead of a clutch, the torque limitercould be a motor brake located at the input of a bi-directional gearbox.The torque limiter could be a motor connected to an asymmetricalinput/output bi-directional gearbox where the efficiency to drive theinput of the gearbox is greater than the efficiency of the gearbox whendriven from the output. The solar tracker may be a push/pull linkedtracker and the torque limiter may be a linear slip device. The solartracker may include a hydraulic system and the torque limiter may be apressure relief valve. In exemplary embodiments, the torque limitingmechanism may be a bi-directional gear drive motor assembly thatback-drives at a pre-determined torque.

In exemplary embodiments, the torque-limiting clutch may be incorporatedinto a plurality of solar trackers connected into an array layoutcomprised of one or more rows of solar trackers. In exemplaryembodiments, one spring is connected to the torque tube or torsion beamat or near the first end of the tracker row, and another spring isconnected to the torque tube or torsion beam at or near the second endof the row. As discussed above, each spring may be incorporated into aspring counter-balance assembly or into a damper or bearing housingassembly. The embodiments discussed above advantageously include lessstress on the drive system of the tracker, less deflection in the torquetube or solar structure, less material needed in the torque tube ortorsion beam if the torsional deflection is controlling the design, andenablement of the use of uncomplicated pivots and structure.

Thus, it is seen that spring counter-balance assemblies, systems, andmethods incorporated into systems such as solar trackers are provided.While the systems, devices, and methods have been described in terms ofexemplary embodiments, it is to be understood that the disclosure neednot be limited to the disclosed embodiments. Although illustrativeembodiments are described hereinabove, it will be evident to one skilledin the art that various changes and modifications may be made thereinwithout departing from the disclosure.

It should be understood that any of the foregoing configurations andspecialized components or chemical compounds may be interchangeably usedwith any of the systems of the preceding embodiments. It is intended tocover various modifications and similar arrangements included within thespirit and scope of the claims, the scope of which should be accordedthe broadest interpretation so as to encompass all such modificationsand similar structures. The present disclosure includes any and allembodiments of the following claims. It is intended in the appendedclaims to cover all such changes and modifications that fall within thetrue spirit and scope of the disclosure.

What is claimed is:
 1. A solar tracker system comprising: a torque tube;a column supporting the torque tube; a solar panel attached to thetorque tube; and a damper assembly having a first end operativelyconnected to the torque tube and a second end operatively attached tothe column.
 2. The solar tracker system of claim 1, wherein the firstend of the counter-balance assembly is connected to the torque tube viaa top bracket, and the second end of the counter-balance assembly isconnected to the column via a bottom bracket.